Urea-formaldehyde molding composition



- Patented Nov. 5, 1940 UREA-FORMALDEHYDE MOLDING COMIPO- SITION AndrewW. Kassay, Toledo, Ohio, assignor to Plaskon Company, Incorporated,Toledo, Ohio, a corporation of Delaware 1 No Drawing. ApplicationSeptember 7, 1938,

3 Claims.

The invention relates to plasticized formaldehyde-urea moldingcompositions.

Formaldehyde-urea molding compositions are thermosetting, i. e., whenmolded under elevated 5 pressure and temperature they first soften andthen harden at the molding temperature. A thermoplastic moldingcomposition, in contrast, remains soft until the molded article hascooled.- Although an article molded from a thermosetting ter arelatively short time and while the article is .l Serial No. 228,825

' composition can be removed from the mold af-- still hot, an articlemolded from a thermoplastic composition cannot be removed from the molduntil it has cooled, and thus hardened sufficiently so that it does notbecome blistered or distorted upon release of the pressure. The lengthof time for which a molding composition must be left in the mold is oneof the factors that determines the cost of articles molded from thecomposition. A composition that must be left in the mold twice as longas another composition requires about twice as much molding equipmentfor the same volume of production, and hot-molding equipment. isexpensive. Although the thermosetting character of forma1dehyde-ureamolding compositions is highly advantageous, the softening of suchcompositions that occurs in the mold before setting or hardening takesplace is very important. A thermosetting composition that does notundergo proper initial softening in the mold cannot be molded properly.For example, an article molded from such a composition may not beproperly homogeneous, and may consist of incompletely softened. granulescemented together. Granular, unfused structure, due to insuflicientsoftening of the composition in the mold, is found most frequently inthe central portions of relatively thick articles, such as knobs andhandles.

Insufficient initial fusing results in an unhomogeneous appearance ofthe finished article, such as a streaked surface in the case of acolored ar- Although acid substances have been used as plasticizers informaldehyde-urea molding compo-- sitions containing no cellulose, suchsubstances cannot-be used in a composition containing cellulose as afiller, because they render it unstable and cause rapid deterioration.Formaldehyde-urea molding compositions containing no cellulose have notbeen found satisfactory for commercial use.

To be suitable for useas a plasticizer, a substance should not be soalkaline as to prevent the formaldehyde-urea molding composition fromhardening in the mold. Substances that are highly soluble in watercannot be used as plasticizers, because they seriously impair theresistant properties of a formaldehyde-urea resin.

Phenol has been suggested as a plasticizer for formaldehyde-urea moldingcompositions, but it is unsatisfactory because it imparts an undesirablecolor and odor to the compositions. Moreover, the color of aformaldehyde-urea composition containing phenol is so unstable that thecomposition would have to be handled in a refrigerated dark room toprevent the appearance of the molded articles from being spoiled.Toluene sulfonamides have been used for want of better plasticizers, buttheir plasticizing effect is so slight that they are of little value.

Only substances that are soluble in formaldehyde-urea resin can be usedas plasticizers, because insoluble substances bleed out of the resin andthus spoil molded articles in which they are used. The substances thatare soluble in formaldehyde-urea resin are very limited in number. Mostof such substances seem to have a molecular structure similar to that ofthe resin; for example, certain urea derivatives'are soluble in formaldehyde-urea resin. However, urea derivatives in general do not haveaplasticizing effect upon formaldehyde-urea molding compositions. Ureaitself cannot be used as a plasticizer because of its deleterious effectupon the product. The substances that are both soluble informaldehydeurea resin and capable of appreciably plasticizing aformaldehyde-urea molding composition are extremely rare.

The principal object of the invention is to provide a formaldehyde-ureamolding composition containing a novel plasticizer. More specificobjects and advantages are apparent from the description, which merelydiscloses and illustrates the invention and is not intended to imposelimitations upon the claims.

A molding composition embodying the invention contains a plasticizerwhich has a melting point of about 102 C., and which can be prepared bytreating dimethylol urea with methyl alcohol. The structural formula oCHz-O-OHg-NH-C-NH-Qlh-O-CH: has been given in the literature for thissubstance, but the correctness of this formula is doubtful.

This plasticizer can be prepared as follows: Dimethylol urea (100 parts)is dissolved in methyl 5 alcohol (300 parts) containing one part ofsuliuric acid, at a temperature below 50 C. The solution is thenneutralized with alcoholic potassium hydroxide, filtered, and evaporatedat 80 C. to one-half of its original volume. When the solution cools,crystals of the plasticizer separate out. They may be filtered and driedat 60 C.

A formaldehyde-urea molding composition of the usual type, consistingprimarily of cellulosic material (40 to 50%) and a formaldehyde-ureareaction product, may be employed.

Example A dried formaldehyde-urea molding composition containing 35parts of alpha-cellulose fiber o impregnated with 50 parts of aformaldehydeurea reaction product is ground in a ball mill, togetherwith 4 parts of a substance prepared as described above. The customarymodifiers, such as lubricants, accelerators, and coloring matter, mayalso be added to the ball mill. After an intimate mixture has beenobtained in the form of a fine powder, it may be granulated or formedinto pellets so that it can be used conveniently for charging molds. Themolding is performed under a suitable pressure at a temperature of aboutVarious applications of the invention may be devised to meet variousrequirements.

Having described my invention, I claim: 1. A thermosetting moldingcomposition comprising a formaldehyde-urea reaction product and aplasticizer which has a melting point of about 102 C., and which issubstantially identical with the substance obtained by dissolving 100parts of dimethylol urea in 300 parts of meth- 5 yl alcohol containing 1part of sulfuric acid, at a temperature below C., neutralizing thesolution with alcoholic potassium hydroxide, filtering, evaporating thesolution at C. to one-half its original volume, and crystallizlng theplasticizer 10 from the solution.

2. A formaldehyde-urea molding composition comprising aformaldehyde-urea reaction product, cellulosic material, and aplasticizer which has a melting point of about 102 C., and which 15 issubstantially identical with the substance obtained by dissolving partsof dimethylol urea in 300 parts of methyl alcohol containing 1 part ofsulfuric acid, at a temperature below 50 C., neutralizing the solution'with alcoholic potas- 2o sium hydroxide, filtering, evaporating thesolution at 80 C. to one-half its original volume, and crystallizing theplasticizer from the solution.

3. A formaldehyde-urea molding composition comprising about 5 per centof a plasticizer which 25 has a melting point of about 102 C., and whichis substantially identical with the substance obtained by dissolving 100parts of dimethylol urea in 300 parts of methyl alcohol containing 1part of sulfuric acid, at a temperature below 50 C., 30 neutralizing thesolution with alcoholic potassium hydroxide, filtering, evaporating thesolution at 80 C. to one-half its original volume, and crystal- ANDREWw. mssay. 35

